A New Type of Dyson Sphere May Be Nearly Impossible to Detec

[Tom Kalbfus]

A New Type of Dyson Sphere May Be Nearly Impossible to Detect

Over fifty years ago, physicist Freeman Dyson proposed an awesome, if slightly insane, idea: That an advanced alien civilization might construct a massive, energy-harvesting sphere around its star, and bunk up inside.

Scientists have never given up on Dyson spheres—we've even conducted a few legitimate searches for their infrared heat signatures. Now, physicists Ibrahim Semiz and Salim Ogur may have an explanation for why we can't seem to find the megastructures. If Dyson spheres exist, they're probably a lot smaller than we thought.

Since Dyson first proposed his massive space habitats, scientists have tried to imagine how such structures could physically work. By and large, researchers have focused on Dyson spheres encircling Sun-like stars. But this scenario poses a few major, and perhaps insurmountable, problems. For starters, such a sphere would have to be built at a distance of roughly 1 AU, the same distance between the Earth and the Sun. That means the structure would be utterly massive, requiring huge volumes of material to construct. What's more, the surface of the sphere would experience only minuscule levels of gravity. To live on it, humans would either need substantial genetic modification, or some sort of advanced artificial gravity system, the likes of which we haven't been able to piece together, even theoretically.

From "Relics," the Star Trek episode that introduced millions to Dyson spheres.

A white dwarf star—the dimmer stellar remnant left over after a Sun-like star swells up and explodes—might be a better option for Dyson spheres. A white dwarf's habitable zone is much closer, so the sphere would end up being significantly smaller. The researchers calculate that a one meter-thick sphere built in the habitable zone of a white dwarf would require 10^23 kilograms of matter, slightly less than the mass of our moon. A Dyson sphere encircling a white dwarf would also have almost Earth-like gravity, according to the researchers' calculations.

There's just one catch: Because white dwarfs are less luminous than Sun-like stars, the infrared heat signatures emitted by a white dwarf Dyson sphere would be much smaller and harder to detect. If intelligent aliens are out there, it may be a while yet before our scopes are powerful enough that we're able spot them from Earth. [arXiv via MIT Technology Review]

Top image via Slawek Wojtowicz




A small footnote: The researchers estimate that a Dyson sphere surrounding a white dwarf would be roughly 10 ^6 kilometers in radius. As pointed out by an astute commentator, this puts the newly proposed Dyson sphere within an order of magnitude of the one featured in Star Trek: The Next Generation. It may be new to science, but it seems Star Trek figured this all out loooong ago.

Contact the author at maddie.stone@gizmodo.com or follow her on Twitter.

As an exercise, how big would the Dyson sphere around this star be, and what would be its surface gravity?
Sirius B
With a mass nearly equal to the Sun's, Sirius B is one of the more massive white dwarfs known (0.98 M☉[102]); it is almost double the 0.5–0.6 M☉ average. Yet that same mass is packed into a volume roughly equal to the Earth's.[102] The current surface temperature is 25,200 K.[7] However, because there is no internal heat source, Sirius B will steadily cool as the remaining heat is radiated into space over a period of more than two billion years.[103]

A white dwarf forms only after the star has evolved from the main sequence and then passed through a red-giant stage. This occurred when Sirius B was less than half its current age, around 120 million years ago. The original star had an estimated 5 M☉[7] and was a B-type star (roughly B4–5)[104][105] when it still was on the main sequence. While it passed through the red giant stage, Sirius B may have enriched the metallicity of its companion.

This star is primarily composed of a carbon–oxygen mixture that was generated by helium fusion in the progenitor star.[7] This is overlaid by an envelope of lighter elements, with the materials segregated by mass because of the high surface gravity.[106] Hence the outer atmosphere of Sirius B is now almost pure hydrogen—the element with the lowest mass—and no other elements are seen in its spectrum.[107]

 

[heron61]

The problem with this is that almost no one is seriously suggesting aliens are making solid Dyson spheres, the stresses on the materials involved in even one around a white dwarf are vast. Instead, Dyson's original idea was for a cloud of constructed habitats and huge solar collectors in solar orbit.

 

[Tom Kalbfus]

The problem with this is that almost no one is seriously suggesting aliens are making solid Dyson spheres, the stresses on the materials involved in even one around a white dwarf are vast. Instead, Dyson's original idea was for a cloud of constructed habitats and huge solar collectors in solar orbit.

They are easier to build than a ringworld! The thing about a white dwarf is when you get into its habitable zone, the gravity pulling inward is significant.

http://www.solstation.com/stars/sirius2.htm

Sirius B

Nicknamed "the Pup" as the much smaller companion to the Dog Star, this much dimmer object is a white dwarf (DA2-5 or A2-5 VII). It is more than 8,200 times fainter than Sirius A and 360 times fainter than Sol.

360 times fainter than Sol eh? That means the radius of the habitable zone around Sirius b is 7,905,694 km, that is quite a big sphere. The inward force of gravity on that sphere would be 0.22304282500536 times that of gravity on Earth by the way, more than on the Moon, less than on Mars, but the escape velocity is so high, it should have no problem holding onto an atmosphere. Generally the best model would be two spheres, a transparent inner sphere to let in light and an outer sphere where people live. People would live on ledges on the outer sphere, mirrors would then reflect light coming up from the star downward onto the inhabited surface.

Alternately you could have a sphere with a number of windows to let light through. Inside the sphere is a series of Fresnel lenses that concentrate light through the windows, the light is focused on convex parabolic mirrors on top of tall towers at least 500 km high or perhaps higher, these mirrors defocus the concentrated light and reflect it back down on the outer surface, call these sun towers if you like, the could be on top of tall artificial mountains rising above the atmosphere (500 km high) The surface can be divided up into a series of hexagons, in the center of which is a window, a sun tower and a reflecting parabolic mirror. Shutters in the window will provide night and day for the world. The warmest part of each hex is toward the center, as you move towards the edges, the climate becomes colder.

 

[Tom Kalbfus]

You know the Sirius System is part of the OTU

1629 Dingir/Solomani Rim Sirius A000769-E As Na Va Pi Pz Mr 210 A1 V D Third Imperium, Domaign of Sol

There are also two other worlds, the D is the white dwarf I mentioned. What if there was a Dyson Sphere there as I mentioned, how would it affect the local area in the OTU, say for instance it was built during the Long Night. The surface gravity is about one fifth that of Earth, and every so often is an evenly spaced sun tower shining the dwarf stars inner light back down upon the outer surface on a 24-hour day/night cycle. Each Sun tower rises above a giant fake volcano who's crater is above the 500 km high standard (6) atmosphere. Plants and animals of this world can be gigantic. This could be the puzzle of the Sirus system, the puzzle being, no one knows who built it.

 

[Reynard]

First off, it's a sphere surrounding the star. Second, it's "a massive, energy-harvesting sphere around its star". Hard to detect if the point of a Dyson is to collect the energy of the sun inside such a frame. Near impossible to detect the sun. Still, power is a cycle that gets used and ends up somewhere. Neither matter OR energy is destroyed. A lot of solar energy received by the Earth is dissipated away back into space while much is used to convert matter such as organic molecules becoming carbon chains to create life forms then stored in the earth in the form of coal. They would not need to store energy with a nearly limitless supply. Organic storage would be a mere byproduct of a artificial biosphere. Even if the majority of the energy powered a massive techno structure (think Coruscant, an ecumenopolis or world city), waste energy would still need to be bled off. That waste might be significantly less and therefore less detectable but we're talking the power of a star system in a tight ball. I'd say something is going to show unless thay go to ludicrous means to hide it.

 

[Tom Kalbfus]

First off, it's a sphere surrounding the star. Second, it's "a massive, energy-harvesting sphere around its star". Hard to detect if the point of a Dyson is to collect the energy of the sun inside such a frame. Near impossible to detect the sun. Still, power is a cycle that gets used and ends up somewhere. Neither matter OR energy is destroyed. A lot of solar energy received by the Earth is dissipated away back into space while much is used to convert matter such as organic molecules becoming carbon chains to create life forms then stored in the earth in the form of coal. They would not need to store energy with a nearly limitless supply. Organic storage would be a mere byproduct of a artificial biosphere. Even if the majority of the energy powered a massive techno structure (think Coruscant, an ecumenopolis or world city), waste energy would still need to be bled off. That waste might be significantly less and therefore less detectable but we're talking the power of a star system in a tight ball. I'd say something is going to show unless thay go to ludicrous means to hide it.

Actually its a small Dyson Sphere 8,000,000 km in radius, I have to make it a little larger, as it intercepts all of Sirius b's direct energy, mostly what this energy is used for is to illuminate the outside of the Dyson Sphere. I've figured out how to get light from the inside of the sphere to the outside. Basically think of it as two nested spheres, the inner one is a sphere made up of Fresnel lenses, that is lenses consisting of an network of mirrors designed to reflect light diagonally towards a focal point, this inner sphere is made up of hexagons consisting of Fresnel lenses.

These are used in light houses and same on material that a regular curved lens would have. This is the interior sphere, the outer sphere has a lot of holes in it, windows with some transparent material. The fresnel lenses on the inside concentrate the sunlight from sirius b through these holes and on top of very tall towers above these holes are convex mirrors.

This diagram shows the light paths coming out of the holes in the outer sphere. On top of this sphere is atmosphere, and terrain (oceans, mountains etc.)

As I said before there are a lot of these windows, surrounded by terrain in a hexagonal pattern around the sphere, the edges of each hexagon are cooler, the centers are warmer. The gravity on the surface in the case of this Dyson is one fifth of the Earth's gravity.

 

[heron61]

If you can make a solid dyson sphere, one of the easiest and best would be an outside dyson shell (http://www.alcyone.com/max/writing/essays/outside-dyson-shells.html). Built it around a small class M (red dwarf) star, which will last for trillions of year, and not only do you have a long-lived habitat, but you can have something like 1G and earth normal temperatures if you are standing on the outside.

More practicaly, I'd go for something like 0.7 Gs, and somewhat lower temperatures & have the rest of the heat made up by using a red dwarf star that was a binary pair with a class K (orange) star, that would provide light and additional warmth that was in a good spectrum for human eyes.

 

[dragoner]

It would be interesting to make a dyson sphere around a red dwarf in a binary system, then you get both the internal heat, and the orbit around a star maybe.

 

[Reynard]

What would be the purpose to make a double sphere then dump the light to an outer surface which, by your description, sends most into space as columns of light. Sounds incredibly wasteful! The idea is to capture all the energy and that should be using the direct surface area.

Speaking about these sun hogs, what would inspire a civilization to ever consider building something consuming ungodly amounts of energy and material? What energy source is used for the massive construction machines? Maybe the same technology to capture sunlight inside such a sphere? I can only assume a Dyson sphere, or a ringworld, would be conceived in a physical universe that has no FTL travel and one is forever isolated. A civilization must have an overpowering need to grow and expand their population. If they survive long enough to advance, they consume their system by making the entire solar system a world. Hopefully they become masters of recycling and energy manipulation, metallurgy and population design. Once the sphere is done, there's nothing else outside. Almost a hive.

 

[Tom Kalbfus]

What would be the purpose to make a double sphere then dump the light to an outer surface which, by your description, sends most into space as columns of light. Sounds incredibly wasteful! The idea is to capture all the energy and that should be using the direct surface area.

Speaking about these sun hogs, what would inspire a civilization to ever consider building something consuming ungodly amounts of energy and material? What energy source is used for the massive construction machines? Maybe the same technology to capture sunlight inside such a sphere? I can only assume a Dyson sphere, or a ringworld, would be conceived in a physical universe that has no FTL travel and one is forever isolated. A civilization must have an overpowering need to grow and expand their population. If they survive long enough to advance, they consume their system by making the entire solar system a world. Hopefully they become masters of recycling and energy manipulation, metallurgy and population design. Once the sphere is done, there's nothing else outside. Almost a hive.

Maybe some races never developed Jump Drive technology.

Well its meant to be a very large artificial world, this one on the Traveller scale is size 1000! Size 8 is Earth-sized. One possibility is it could serve as the capital of a very large interstellar empire, as you know the capital of the Imperium is a smallish size 5 world. As for harvesting energy, about half the energy is used to illuminate half the sphere on the outside, the other half may be used for other things, such as the production of antimatter for instance. The surface area is that of one million size A worlds. About one third the surface area of Larry Niven's Ringworld and much easier to build. The point of it is to make use of both the star's gravity and its light, it just so happens that for Sirius b the habitable zone corresponds to the radius for 1/5th Earth Gravity, it is not perfect for humans, actually it would be a fitting habitat for a race of 10 meter tall humanoid giants, they would have 125 times the mass of a human , but under 1/5th gravity only 25 times the weight and their muscular cross-section would give then 25 times the strength. Since the Traveller scale for strength is linear, that would be from 50 to 300 with a 2d6 roll times 25, they would be proportioned the same as a human as opposed to a dinosaur or an elephant.

 

[Condottiere]

Bob Shaw's Orbitsville postulates that it's bait made by a pre-existing interstellar civilization, to let successive civilizations that achieve interstellar travel expend their energies trying to colonize it.

 

[Tom Kalbfus]

If you can make a solid dyson sphere, one of the easiest and best would be an outside dyson shell (http://www.alcyone.com/max/writing/essays/outside-dyson-shells.html). Built it around a small class M (red dwarf) star, which will last for trillions of year, and not only do you have a long-lived habitat, but you can have something like 1G and earth normal temperatures if you are standing on the outside.

More practically, I'd go for something like 0.7 Gs, and somewhat lower temperatures & have the rest of the heat made up by using a red dwarf star that was a binary pair with a class K (orange) star, that would provide light and additional warmth that was in a good spectrum for human eyes.

Sirius b is relatively nearby, so we might as well use it, and it has the mass of our Sun in a package the size of Earth. We could not build a similar shell around our own Sun and have it remain habitable, if we build it at that size around a red dwarf it would have miniscule gravity, whereas the Sirius b white dwarf has 1/5th Earth's gravity, which is more than out Moon has at its surface, we could make it smaller but it would be unbearably hot in Sirius b's case. one could build a Dyson shell around a gas giant, but then one wold get very little energy from that gas giant, but their are some gas giants within the habitable zone of certain stars.

 

[Tom Kalbfus]

Bob Shaw's Orbitsville postulates that it's bait made by a pre-existing interstellar civilization, to let successive civilizations that achieve interstellar travel expend their energies trying to colonize it.

Maybe so, that would explain why they built it during the Long Night, when no one was looking!

 

[Tom Kalbfus]

It would be interesting to make a dyson sphere around a red dwarf in a binary system, then you get both the internal heat, and the orbit around a star maybe.

The difference between red dwarfs and white dwarfs is that white dwarfs have much more mass, but give off a similar amount of light. Red dwarfs have fusion going on in their cores, white dwarfs do not, they are just radiating away stored heat, as it has limited surface area through which it can radiate away its internal heat, compared to its mass. A Red Dwarf just has about 80 Jupiters of mass or more, our Sun has about 1000 Jupiters with of mass more or less. White dwarfs gradually cool down over time so their habitable zones shrink.

Another interesting thing about white dwarfs is they can go supernova, a type 2 Supernova to be precise. You see there is a certain maximum limit for a white dwarf's mass, if that mass goes over, the white dwarf's core will collapse into a neutron star shedding its outer layers in a gigantic explosion, this is not caused by a star getting old, but by a white dwarf accumulating too much mass. Type 2 supernovas are a standard candle for measuring the expansion rate of the Universe, because only a white dwarf just under its critical mass going just over its critical mass will cause a type 2 supernova, this could happen to Sirius b if another star collided with it, or it it just sucked up enough interstellar gas, and white dwarfs are fairly common.

 

[heron61]

We could not build a similar shell around our own Sun and have it remain habitable, if we build it at that size around a red dwarf it would have miniscule gravity

Actually, the page I linked to describes how if you build it around a small enough red dwarf, you can get habitable temperatures and 1 G gravity on the outside of a dyson sphere. If you can manage light by some means (a binary star system, using some fraction of the vast amounts of energy you can collect from the star to run lights, or whatever), you've got a sphere around two million km in diameter which has earth-like temperatures and gravity on the outside (no artificial gravity needed). Supply truly insane amounts of soil, water, and air, and you've got something that functions like a planet, but with a surface area more than 24,000 times that of Earth. In short, you could fit pretty much the entire population of the Third Imperium on that world.

 

[dragoner]

Supply truly insane amounts of soil, water, and air, and you've got something that functions like a planet, but with a surface area more than 24,000 times that of Earth.

Imagine that as a planetary romance, talk about "Big Planet".

 

[Tom Kalbfus]

We could not build a similar shell around our own Sun and have it remain habitable, if we build it at that size around a red dwarf it would have miniscule gravity

Actually, the page I linked to describes how if you build it around a small enough red dwarf, you can get habitable temperatures and 1 G gravity on the outside of a dyson sphere. If you can manage light by some means (a binary star system, using some fraction of the vast amounts of energy you can collect from the star to run lights, or whatever), you've got a sphere around two million km in diameter which has earth-like temperatures and gravity on the outside (no artificial gravity needed). Supply truly insane amounts of soil, water, and air, and you've got something that functions like a planet, but with a surface area more than 24,000 times that of Earth. In short, you could fit pretty much the entire population of the Third Imperium on that world.

I guess a star would have to be dim in order to have a habitable zone at the 1-g radius. So what is the habitable zone of Proxima Centauri and what is the gravity level if you build a star there? I'd say both Proxima and Sirius b are available. Sirius b has more white light of course, one can filter out the excess UV rays through the windows

 

[heron61]

I guess a star would have to be dim in order to have a habitable zone at the 1-g radius. So what is the habitable zone of Proxima Centauri and what is the gravity level if you build a star there? I'd say both Proxima and Sirius b are available. Sirius b has more white light of course, one can filter out the excess UV rays through the windows

Yep, you need an M9V star to manage that. Proxima Centauri is an M5V star with 11.3 x the Luminosity and 1.64 x the mass of an M9V star. So, the dyson sphere would need to be 3.3 times the diameter to be at a habitable temperature, giving it a surface gravity of 0.145 G - slightly less than Lunar gravity.

 

[Hopeless]

What if they could only build something like this on a limited level?

Think instead of Dyson Sphere but say a Battle Planet or Death Star?

You could have one already in the solar system but wouldn't know it unless someone went and investigated in person!

And yes this is a thread about Dyson Spheres but it doesn't necessarily have to be that big you're assuming all life would be of similar size to ourselves and that isn't necessarily the case now wouldn't it?

 

[Tom Kalbfus]

I guess a star would have to be dim in order to have a habitable zone at the 1-g radius. So what is the habitable zone of Proxima Centauri and what is the gravity level if you build a star there? I'd say both Proxima and Sirius b are available. Sirius b has more white light of course, one can filter out the excess UV rays through the windows

Yep, you need an M9V star to manage that. Proxima Centauri is an M5V star with 11.3 x the Luminosity and 1.64 x the mass of an M9V star. So, the dyson sphere would need to be 3.3 times the diameter to be at a habitable temperature, giving it a surface gravity of 0.145 G - slightly less than Lunar gravity.

Seems like Sirius b is more attractive, it is close 8.611 light years, (about twice as far as alpha centauri) and it has the mass of our Sun (1.03 solar masses)

http://en.wikipedia.org/wiki/Sirius

Sirius is a binary star system consisting of two white stars orbiting each other with a separation of about 20 astronomical units (3.0×109 km; 1.9×109 mi)[note 7] (roughly the distance between the Sun and Uranus) and a period of 50.1 years. The brighter component, termed Sirius A, is a main-sequence star of spectral type A1V, with an estimated surface temperature of 9,940 K.[8] Its companion, Sirius B, is a star that has already evolved off the main sequence and become a white dwarf. Currently 10,000 times less luminous in the visual spectrum, Sirius B was once the more massive of the two.[94] The age of the system has been estimated at around 230 million years. Early in its lifespan it was thought to have been two bluish white stars orbiting each other in an elliptical orbit every 9.1 years.[94] The system emits a higher than expected level of infrared radiation, as measured by IRAS space-based observatory. This may be an indication of dust in the system, and is considered somewhat unusual for a binary star.[92][95] The Chandra X-ray Observatory image shows Sirius B outshining its bright partner as it is a brighter X-ray source.[96]

The dust in the system is an indicator that there may be lots of material to build with, it is 230 million years old, so there may be lots of planetesimals in the system, The main thing though is complex intelligent life will probably never evolve in this system, so we can remake it however we like, whereas a red dwarf has an expected lifespan of about hundreds of billions of years, life could certainly evolve around a red dwarf. Another disadvantage of Proxima is that it is a flare star, though if completely surrounded by a Dyson Sphere, that might not matter. There probably are cooler white dwarfs where you could have a 1-g sphere in the habitable zone, although I believe Sirius b is the closest white dwarf to Earth Sirius a has a problem in that Sirius b disrupts orbits in a's habitable zone, Sirius b's habitable zone, which is 8 million km out for the equivalent amount of sunlight that Earth's receives is not so affected. And there are probably the cold remnants of the planetary nebula that formed when Sirius b went nova and blew its outer layers into space, there is probably a solar mass worth of material out there, maybe in the form of comets. My comment earlier about the sphere being a size 1000 world, its actual a size 10,000 world with a diameter of 16 million kilometers, it has 1000 times the diameter of a size 10 world and 1 million times its surface area. It is easier to build that a ringworld, a ringworld has to hold itself together against its own centripedal force, and there is no inward force that works very well for a class G2 V star, the best I can think of is having a stationary ring with the mass of our Sun on the outside of the rotating ring, either that or we discover some unknown material with the bonding strength of an atomic nucleus! The Sirius b Dyson will give you about that much surface area, but we don't need "unobtainium" to hold it together, Sirius b's gravity does that for us, all we need to do is counteract the inward pull of Sirius' gravity with some outward centrifugal force. Within the shell, we could have a series or rotating rings all at different planes or rotation pushing outward on the shell to counteract its weight against gravity. This Dyson sphere is made out of ordinary matter, probably carbon. There are a bunch of maglev tracks within the shell where counterweights are rotated for their outward centrifugal force, but the sphere itself rotates only slowly, maybe once every 360 days perhaps. The sun towers hold up mirrors which reflect light from Sirius B shining through the windows back onto the outer surface of the sphere. The light windows would probably be 50 km above the sphere's sea level, this is to put it above most of the weather in the troposphere. The tower holding up the convex mirror would be above that. People below it would see an image of Sirius b in that mirror shining down on them, the shutters in the floor window open and close giving a 24 hour day/night cycle.

Now at 0.2 Earth gravity, what can we put on its surface? How about some giants? We could have some giant sized humans 10 meters tall, trees that rise to 100 meters to 150 meters above the surface, everything could be enlarged to 5 times the size of what you would expect on Earth, and even for these giants, there would be a lot of space for them to roam around on this Dyson, where normally they would be confined to small worlds about the size of out moon. I think the giant flora and fauna on this world's surface is what makes it interesting. I think such a giant would have to be 25 times as strong as a human, I think dexterity would be lower than in a normal human, as having such an enormous body with long limbs would tend to slow down its reaction speed. When it walks it would take slow ponderous steps in the 1/5th Earth's gravity, and normal humans would be leaping around like rabbits in comparison. I guess you could say the intelligent giants are probably the builders of this world, or they built the machines which built it at least.

What if they could only build something like this on a limited level?

Think instead of Dyson Sphere but say a Battle Planet or Death Star?

You could have one already in the solar system but wouldn't know it unless someone went and investigated in person!

And yes this is a thread about Dyson Spheres but it doesn't necessarily have to be that big you're assuming all life would be of similar size to ourselves and that isn't necessarily the case now wouldn't it?

Yes you probably can build an artificial planet, the Death Star is about the size of a large asteroid, so that is definitely doable as well.